At Last! an Answer to the Question: How Far Should My Elbow Bend?

"Normal Range of Motion Reference Values"
E-Hand.com: the Electronic Textbook of Hand Surgery (undated)

"Typical Range of Motion
"Elbow Extension/Flexion 0/145...."

The data is in a table, and tells how far the elbow, Forearm, Wrist, Thumb basal joint, Thumb Interphalangeal and Metacarpophalangeal joints, and finger DIP,PIP and MCP joints should bend.

Think of it as part of a spec sheet for the lower part of the human arm. Sure, it's not the sort of thing you'll bring up in conversation all that often: but I think it's interesting.

Of course, I think that quite a few things are interesting, that other people don't.